(1) Field of the Invention
The present invention relates to the field of window shades or roller blinds. The subject of invention is a mechanism controlling the rotation of roller blinds winding roller with a spring drive, especially window blinds, when rolling or unrolling the sunshade.
(2) Description of the Related Art
There are known restraining devices containing a decelerating structure, connected with roller blinds having spring drive. These are generally described as toothed planetary gear units with a central wheel, planet wheels and ring gear. A rotor is joined with the central wheel and planet wheels are rotationally seated on a unidirectional coupling, while the ring gear is rotationally joined with a roller, hollowed along its entire length, the two ends of which are rotationally joined with a couple of bearing pivots. The edge of the sunshade is attached to the roller, and inside the roller there is an immobile middle rod, joined to one of the bearing pivots. A spring, functionally adjusted to impart rotation of the roller in a first direction round its axis with pull on the sunshade, is joined with the middle rod and with the roller. In the roller there is located a fluid brake, functionally connected with the roller and middle rod, restraining rotation of the roller in its first direction. A chamber of the liquid brake is rotationally joined with the roller.
The problem with these known restraining devices is that their endurance is low.
U.S. Pat. No. 4,513,805 to Mase discloses a mechanism for controlling rotation of a roller blind comprising a fixed shaft 2, a stator 4, a rotator 7, a center shaft 8, a rotary shaft 17, a tube 1, a ring gear 13, a brake drum 18, a gearing cover 14, brake shoes 23, absorbing rubber 25, arcuate weights 22, axes 11, planet gear 12, sun gear 16, arm 19, and pins 21.
The Mase solution is based on completely different principles of operation and construction than the instant invention. In the Mase solution the speed of the roller shade is increase through the planetary gear and the increased speed is transmitted to the holder, on which are mounted oscillating weights. Under the influence of centrifugal force the weights diverge outwardly and press on the braking surfaces of the sleeve. The higher the roller shade speed, the greater the braking force.
Development of a restraining device with higher endurance represents a great improvement in the field of roller binds and satisfies a long felt need of the roller blind customers.